Display device having a connection area outside the display area

ABSTRACT

An object of the present invention is to provide aA display device capable of narrowing the area of the frame. In order to achieve this object, the display device according to the present invention  has a substrate having a plurality of arranged display elements and a wiring layer of a power source on the peripheral side; a bank layer for mutually separating the display elements; an electrode layer for covering the plurality of display elements and the bank layer; and a sealing substrate for further covering the electrode layer by joining the peripheral portion of the substrate and the sealing portion circling around the periphery via a joining element such as an adhesive; wherein the  adhesive. The periphery of the sealing substrate is positioned inside the periphery of the substrate, and the peripheral portion of the electrode layer is connected to the wiring of the power source within the sealing portion.

This is one of two reissue applications of U.S. Pat. No. 7,190,116. Thisreissue application is a reissue of U.S. Pat. No. 7,190,116. The secondreissue application is a reissue continuation of this reissueapplication, the disclosure of which is incorporated by reference hereinin its entirety.

This is a divisional application of U.S. application Ser, No.10/341,392, filed on Jan. 14, 2003 now U.S. Pat. No. 7,038,377.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a flat, panel-type display device, andin particular to an invention of a display device capable of narrowingthe so-called frame, which is the non-display area at the periphery of adisplay unit.

2. Description of the Related Art

There has been provided a display device that forms screens of text,images or video pictures by arranging a plurality of display elementsand controlling the status of the respective display elements. Anexample of this would be an electro-optic device such as a liquidcrystal display device or an organic EL display device. With this kindof display device, deterioration of components is prevented byhermetically sealing a substrate and another substrate, or a substrateand a sealing member.

For instance, with an organic EL display device, the peripheral gasinfiltrating within the device influences the life duration of theorganic EL light emitting element. In particular, moisture (water vapor)and oxygen deteriorate metal electrodes, and complicate the prolongedoperation of the light emitting element. Thus, a substrate having formedthereon an array of the organic EL display element is sealed with thelikes of a metal can, waterproof plastic package or protective film toacquire gas barrier property against water vapor and oxygen.

Nevertheless, when forming the likes of a sealing metal can or sealingprotective film on a display element substrate with display elementsformed thereon, space is required for connecting the sealing metal canor sealing protective film to the display element substrate. Moreover,in order to secure the foregoing gas barrier property, a prescribedamount of connection width (connection space) also becomes necessary.Since the sealing of the display element substrate is conducted at theperiphery of this substrate, a so-called frame that is not utilized as adisplay area arises at such periphery. This complicates theminiaturization and unrestricted design of devices such as portabletelephone devices and portable information devices mounted with adisplay device.

Accordingly, an object of the present invention is to provide a displaydevice capable of narrowing the area of the frame.

Moreover, another object of the present invention is to provide adisplay device in which the gas barrier property does not deteriorateeven upon narrowing the area of the frame.

SUMMARY OF THE INVENTION

In order to achieve the foregoing objects, the display device accordingto the present invention comprises: a substrate having a plurality ofdisplay elements separated with a bank layer, and a wiring layer; anelectrode layer for covering the plurality of display elements and thebank layer; and a sealing substrate for covering the substrate byjoining at least the peripheral sealing area of the substrate; whereinthe wiring layer is formed at a part of the sealing area of thesubstrate; and the peripheral portion of the electrode layer isconnected to the wiring layer within the sealing area.

According to the foregoing structure, since a part of the sealing areaof the substrate can be utilized as the connection area of the electrodeand wiring, the size of the sealing substrate can be reduced whilesecuring the connection width necessary for gas barrier or the like, andthe portion that is the structural element of the frame of the displaydevice is thereby reduced in size.

Preferably, the electrode layer is a common electrode (negativeelectrode or positive electrode) of the respective display elements.

Preferably, the common electrode layer is formed to include at least twotypes of electrode layers in which one is a lower layer positioned onthe display element side and the other is an upper layer positionedthereon; and the upper electrode layer is formed from material havingsuperior gas barrier property or anti-environmental property incomparison to the upper electrode layer. Thereby, deterioration of thelower electrode layer can be suppressed. Moreover, a film with favorableluminous efficiency (or operational efficiency) can be used as the lowerelectrode layer.

Preferably, the lower electrode layer is formed to cover the pluralityof display elements in their entirety and at least a part of the banklayer, but away from the sealing portion of the sealing substrate; andthe upper electrode (layer) is formed to cover the lower (part)electrode layer in its entirety and to reach inside the sealing portionof the sealing substrate. Thereby, the lower electrode layer will beaway from the joining portion where gas may infiltrate, and it willthereby be possible to suppress the deterioration of the lower electrodelayer. Moreover, a film with favorable luminous efficiency can be usedas the lower electrode layer.

Preferably, the sealing substrate includes a protrusive sealing portionso as to circle around the periphery of the sealing substrate oppositeto the sealing area of the substrate. Thereby, a hollow scalingsubstrate (having a concave cross section) may be used for sealing thesubstrate.

Preferably, the top face of the wiring layer of the substrate is formedflatly, and the electrode layer is laminated thereon and connectedelectrically. Thereby, conduction of the wiring layer and electrodelayer can be sought with certainty.

Preferably, the face of the substrate opposite the sealing portion ofthe sealing substrate is also formed flatly. Thereby, the stress appliedto the sealing portion of the substrate can be made uniform.

Preferably, multilayer thin films are used instead of the sealingsubstrate for sealing. Thereby, a flexible film-like display device canbe realized.

Preferably, the size of the sealing area of the substrate is determinedwith the margin necessary in securing the gas barrier properly oranti-environmental property of the joining means, and the connectionarea of the electrode layer and the wiring layer is included in themargin. Thereby, reliability can be secured and the frame of the displaydevice can be narrowed.

Preferably, the joining means includes an adhesive film, and the filmthickness of the adhesive film does not exceed 20 μm. Moreover, thewidth of the adhesive film is at least 1 mm or more. Thereby, thecontact face with outside atmosphere can be reduced, the infiltrationlength of outside atmosphere can be secured considerably, and thedeterioration of the sealed element can be suppressed thereby.

Preferably, the periphery of the sealing substrate is positioned insidethe periphery of the substrate in an amount corresponding to the marginupon mounting the sealing substrate on the substrate. Thereby, thesealing substrate can be mounted on the substrate with ease.

Moreover, preferably, the periphery of the sealing substrate ispositioned inside the periphery of the substrate in an amountcorresponding to at least the scribe margin upon dividing the substrate.Thereby, space necessary for separating and cutting the display afterassembly is secured.

Preferably, the sealing substrate is structured from a flat substrate.Thereby, sealing can be performed more easily.

Preferably, the bank layer is not positioned within the sealing area ofthe substrate. Thereby, since the bank layer will be away from thesealing area, the bank layer may be formed from an organic materialhaving high moisture permeability.

Preferably, the substrate is a polygonal or a square substrate, and theelectrode layer and the wiring layer are connected at one side of thissubstrate. Thereby, since it will no longer be necessary to lay wiringwith the electrode layer in the other sides (or three sides), such othersides (or three sides) can be narrowed. This kind of structure iseffective in cases as with a display device of a portable telephonewherein the module may be elongated in a certain direction, but isrestricted in other directions.

Preferably, the substrate is a polygonal or a square substrate, and theelectrode layer and the wiring layer are respectively connected at twosides of this substrate. This kind of structure is effective in cases ofinstalling a plurality of driver ICs in order to reduce wiringresistance up to the electrode and displaying large volumes of data.

Preferably, the substrate is a polygonal or a square substrate, and theelectrode layer and the wiring layer are respectively connected at threesides of this substrate. This kind of structure is capable ofsufficiently reducing the wiring resistance up to the electrode throughconnection at such three sides, and seeking the connection with anexternal circuit with one side.

Preferably, the substrate is a polygonal or a square substrate, and theelectrode layer and the wiring layer are respectively connected at foursides of this substrate. This kind of structure is preferable in casesof reducing the wiring resistance as much as possible, which becomesnecessary when realizing a large-sized high resolution display device.Here, a pullout wiring may be formed via an insulation film below thepower source wiring layer, or the connection area of the electrode layerand power source wiring layer may be divided into a plurality of blocks,and the pullout wiring may be disposed collectively between the mutualblocks.

Preferably, dummy display elements are disposed around the periphery ofthe area where the plurality of display elements is arranged. Thereby,substantial influence on the display elements is alleviated. Moreover,application (amount of application) of the display element material withthe inkjet system can be made uniform.

Preferably, the display element is an organic EL element. The lowerelectrode layer is calcium and the upper electrode layer is aluminum.

Preferably, the bank layer is formed from resin material. Color mixturecan be prevented since a bank layer exists between the display elements.

Preferably, the display device is employed in electronic devices such asa digital camera, personal computer, flat-panel television, portableinformation terminal device, portable telephone device, electronic book,and the like. Thereby, various devices with minimal excess non-displayareas (frame) at the periphery of the display device are obtained.

The manufacturing method of a display device according to the presentinvention comprises: a step of forming at least a wiring layer at a partof the sealing area established inside the periphery of the substrate towhich an electrical circuit is to be formed; a step of forming anelement separation layer comprising a plurality of grooves for mutuallyseparating the plurality of display elements excluding the top (face) ofthe wiring layer of the substrate; a step of forming the displayelements to each of the plurality of grooves of the element separationlayer; a step of forming a common electrode layer on the plurality ofdisplay elements, the display separation layer, and the wiring layer,respectively; a joining material application step of applying joiningmaterial to the sealing area of the substrate; and a sealing step ofjoining a sealing substrate having a circular sealing portion at thesealing area of the substrate with the joining material and sealing thesubstrate.

According to the foregoing structure, the frame of the display devicecan be narrowed.

Preferably, the joining material application step applies the joiningmaterial on the connection area of the common electrode layer and thewiring layer formed within the sealing area of the substrate and to theremaining sealing area (other than the foregoing area). Thereby, thesealing area between the substrate and the sealing substrate can besealed with the required joining material.

Moreover, the manufacturing method of a display device according to thepresent invention comprises: a step of forming at least a wiring layerat a part of the sealing area established inside the periphery of thesubstrate to which an electrical circuit is to be formed; a step offorming an element separation layer comprising a plurality of groovesfor mutually separating the plurality of display elements excluding thetop (face) of the wiring layer of the substrate; a step of forming thedisplay elements to each of the plurality of grooves of the elementseparation layer, a step of forming a common electrode layer on theplurality of display elements, the display separation layer, and thewiring layer, respectively; a joining material application step ofapplying joining material to the sealing area of the substrate and thecommon electrode layer; and a sealing step of joining a sealingsubstrate covering the sealing area of the substrate and the commonelectrode layer with the joining material and sealing the substrate.

According to the foregoing structure, the frame of the display devicecan be narrowed.

Moreover, the manufacturing method of a display device according to thepresent invention comprises: a step of forming at least a wiring layerat a part of the sealing area established inside the periphery of thesubstrate to which an electrical circuit is to be formed; a step offorming an element separation layer comprising a plurality of groovesfar mutually separating the plurality of display elements excluding theupper (face) of the wiring layer of the substrate; a step of forming thedisplay elements to each of the plurality of grooves of the elementseparation layer; a step of forming a common electrode layer on theplurality of display elements, the display separation layer, and thewiring layer, respectively; and a sealing step of forming a multilayerfilm on the substrate for covering the sealing area and the commonelectrode layer and sealing the substrate.

Preferably, the multilayer film contains a film that prevents thepermeation of water or gas.

Preferably, the common electrode layer is formed to include at least twotypes of electrode layers in which one is a lower layer positioned onthe display element side and the other is an upper layer positionedthereon; and the upper electrode layer is formed from material havingsuperior gas barrier property or anti-environmental property incomparison to the lower electrode layer. Thereby, deterioration of thelight emitting element can be prevented.

Preferably, the lower electrode layer is formed to cover the pluralityof display elements in their entirety and at least a part of the banklayer, but away from the sealing portion of the sealing substrate: andthe upper electrode layer is formed to cover the lower electrode layerin its entirety and to reach inside the sealing portion of the sealingsubstrate. Thereby, deterioration of the lower electrode layer can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view for explaining the first embodiment of the displaydevice according to the present invention;

FIG. 2 is a cross section along section A-B of FIG. 1 for explaining thefirst embodiment (example of employing a sealing substrate) of thedisplay device according to the present invention;

FIG. 3 is a cross section along section C-D of FIG. 1 for explaining thefirst embodiment of the display device according to the presentinvention;

FIG. 4 is an explanatory diagram for explaining the edge structure of ageneral display device (comparative example) for explaining the effectof the first embodiment;

FIG. 5(a) and FIG. 5(b) are explanatory diagrams for explaining theflatness in the sealing portion of the substrate periphery, wherein FIG.5(a) illustrates a case when there is misalignment between the substratewiring layers 121, 112, 107 and the common electrode 123, and FIG. 5(b)illustrates a case when there is no such misalignment;

FIGS. 6(a)-6(d) are process charts for explaining the manufacturingprocess of the display device according to the first embodiment;

FIG. 7 is a cross section along section A-B of FIG. 1 for explaining thesecond embodiment (example of adhering the entire face of the sealingsubstrate) of the display device according to the present invention;

FIG. 8 is a cross section along section C-D of FIG. 1 for explaining thesecond embodiment of the display device according to the presentinvention;

FIGS. 9(a)-9(d) are process charts for explaining the manufacturingprocess of the display device according to the second embodiment;

FIG. 10 is a cross section along section A-B of FIG. 1 for explainingthe third embodiment (example of employing a multilayer sealing film) ofthe display device according to the present invention;

FIG. 11 is a cross section along section C-D of FIG. 1 for explainingthe third embodiment of the display device according to the presentinvention;

FIGS. 12(a)-12(d) are process charts for explaining the manufacturingprocess of the display device according to the third embodiment;

FIG. 13 is a plan view for explaining the fourth embodiment (example ofemploying dummy pixels) of the display device according to the presentinvention;

FIG. 14 is an explanatory diagram for explaining an example ofconnecting the power source wiring and common electrode at three sidesof the substrate;

FIG. 15 is an explanatory diagram for explaining an example ofconnecting the power source wiring and common electrode at one side ofthe substrate;

FIG. 16 is an explanatory diagram for explaining an example ofconnecting the power source wiring and common electrode at two sides ofthe substrate;

FIG. 17 is an explanatory diagram for explaining an example ofconnecting the power source wiring and common electrode at four sides ofthe substrate;

FIG. 18 is an explanatory diagram for explaining an example of aportable personal computer employing the display device according to thepresent invention;

FIG. 19 is an explanatory diagram for explaining an example of aportable telephone device employing the display device according to thepresent invention;

FIG. 20 is an explanatory diagram for explaining an example of a digitalcamera employing the display device according to the present invention;and

FIG. 21 is an explanatory diagram for explaining an example of anelectronic book employing the display device according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are now explained with reference tothe drawings.

FIG. 1 to FIG. 3 are explanatory diagram for explaining the firstembodiment of the display device according to the present invention.FIG. 1 is a plan view schematically showing the display device. FIG. 2is a cross section schematically showing the cross section alongdirection A-B of FIG. 1. FIG. 3 is a cross section schematically showingthe cross section along direction C-D of FIG. 1. The same referencenumerals are given to the components corresponding in the respectivediagrams. Moreover, the display element area in the center of FIG. 2 isillustrated in a simplified manner.

The display device 1 of the first embodiment shows a case of an organicEL display device. When classified broadly, this display device 1 isstructured from a TFT substrate 100 comprising a light emitting elementarray, a sealing substrate 200 for sealing the light emitting elementarray, a joining means 301 for joining the TFT substrate 100 and sealingsubstrate 200, a scan line driving unit 140 for driving the scan line ofthe TFT substrate 100, a data driver IC 401 for driving the data line ofthe TFT substrate 100, and so on.

The TFT substrate 100 is structured from a plurality of organic EL lightemitting elements 120 arranged in a matrix, a TFT transistor 130 fordriving such light emitting elements 120 or which functions as a switch,and so on. With the TFT substrate 100, a protective film 102 is formedon a glass substrate 101, silicon is deposited thereon,low-concentration impurities are injected therein and patterning isperformed thereto in order to form a polysilicon TFT area 103. Moreover,the substrate 100 may also be a resin substrate. A gate insulation film104 formed of oxidized silicon is deposited thereon with the CVD method.Aluminum is deposited thereon with the sputtering method and patterningis performed thereto in order to form organic EL driving power sourcewiring films 105 and 106, an organic EL negative electrode wiring layer107, and a gate wiring film 108 of the TFT 130. Next, a mask is used toinject high-concentration ion into the source drain area of the TFT area103, and oxidized silicon is deposited thereon in order to form a firstinterlayer insulation film 110. A contact hole mask is used to performanisotropic etching in order to open a contact hole in the TFT area 103.Next, aluminum is deposited thereon and pattering is performed theretoin order to form a source drain electrode 109 and a connection electrode112. Next, oxidized silicon is deposited thereon in order to form asecond interlayer insulation film 111. In order to suppress the arrivalof TFT deterioration factors such as metal ion and water at the TFT, asthe second interlayer insulation film, for example, used may be aninsulation film containing at least one element among boron, carbon,nitrogen, aluminum, silicon, phosphorus, ytterbium, samarium, erbium,yttrium, gadolinium, dysprosium, neodymium, and so on. A display elementgroup described later is formed thereon.

The center area of the TFT substrate 100 structured as described aboveis the display area to which the display element group is disposed. Thelight emitting element 120 of red emission, green emission and blueemission as the display element is arranged in a matrix with these threecolors as a single pixel. Each of the emitted lights of the respectivelight emitting elements 120 is emitted outside via the glass substrate101. Moreover, light may also be abstracted from the side opposite theTFT substrate 100. Here, it is preferable that the layers above thelight emitting layer is structured of material having high opticaltransmittance. In order to separate the respective light emittingelements and prevent color mixture, a bank layer 113 is formed betweenthe respective light emitting elements and at the periphery of thedisplay area. This bank layer 113 may be formed, for instance, bypatterning an organic material film such as a photoresist.

The light emitting element 120 is structured from a transparent (ITO)positive electrode 121, an organic EL layer/electron hole transportlayer 122, a negative electrode (common electrode) 123, and so on. Thenegative electrode 123 has a two-layer structure, and, for example, thelower layer is a calcium film 123a and the upper layer is an aluminumfilm 123b. The negative electrode 123a is formed across the respectivelight emitting elements 120, the bank layers mutually between therespective light emitting elements 120, and the bank layer 113 at theperiphery of the display area, and, the contact with the upper layernegative electrode 123b is secured thereby. The upper layer negativeelectrode 123b also functions as a wiring film, and is connected to thewiring film 107 in the area at the lower part of the sealing portion202. As described above, the luminous efficiency can be improved bymaking the negative electrode 123a, which is in contact with the organicEL layer/electron hole transport layer 122, a calcium film, and, bycovering the calcium film 123a in its entirety with the upper layeraluminum film 123b, low-resistance wiring and gas barrier (erosionprevention) are sought. Moreover, this may also employ an organic ELelement structure where an electron injection layer or an electrontransport layer is additionally disposed on the light emitting layer(organic EL layer/electron hole transport layer), or a laminate of suchelectron injection layer and electron transport layer may beadditionally disposed thereon.

The top face of the substrate 100 structured as described above issealed with a sealing substrate 200 having a cross inverted concaveshape. This sealing substrate 200 is structured, for instance, frommetal, glass, ceramic, plastic or the like, and comprises a tabularsealing plate 201, a protrusive sealing portion 202 formed around theperiphery at the bottom face of this sealing plate, and a drying agent(material) 203. The drying agent 203 adsorbs the water vapor or oxygengas infiltrating inside.

Nitrogen gas as the inert gas is filled between the TFT substrate 100and the sealing substrate 200, and both substrates 100 and 200 arejoined at the sealing portion 202 via an adhesive 301 as the joiningmeans. Although the adhesive may be suitably selected from those havingthermosetting properties or ultraviolet curing properties, inparticular, those having low permeability against gas such as watervapor are employed.

As shown in FIG. 2, the substrate 100 is provided with a margin a forplacing the sealing substrate 200. Moreover, width d of the sealingportion 202 of the sealing substrate 200; that is, sealing area d of thesubstrate 100, is set to a suitable width (corresponds approximately towidth b of the portion of only the adhesive 301 and the connection widthc of the vertical wirings) for the adhesive 301 to prevent theinfiltration of gas. For instance, this width (width d of the adhesive301) is made to be 1 mm or more so as to secure a long infiltrationlength of the outside atmosphere, whereby the infiltration of watervapor and oxygen gas from the adhesive layer will become difficult.Moreover, the film thickness of the adhesive 301 is made to be 20 μm orless so as to reduce the contact face of the adhesive 301 and outsideatmosphere, whereby the infiltration of gas will become difficult. Thiswill also suppress the deterioration of elements sealed inside.

The negative electrode film 123b is placed within the area at the lowerpart of this sealing portion 202 in an amount corresponding to thevertical connection width c, and connected to the wiring 107 of thesubstrate 100 via the ITO film 121 and the source drain electrode film112.

As shown in FIG. 3, the data line of the substrate 100 is connected tothe electrode 121 of the substrate end, and connected to a wiring tape402 via an anisotropic conductive film 303. The data driver IC 401 fordriving the respective data lines is bonded in the middle of this wiringtape. A part of the negative electrode 123 is also placed into thesealing portion 202 at the lower part of the substrate 100.

FIG. 4 shows a general joining example (comparative example) of the TFTsubstrate 100 and the sealing substrate 200. In FIG. 4, the componentscorresponding to those illustrated in FIG. 2 are given the samereference numerals, and the explanation of such components is omitted.

in this example, a mounting margin a upon mounting the sealing substrate200 on the TFT substrate 100 and a margin d of the adhesive 301 forpreventing the infiltration of gas and securing reliability of sealingare secured outside the connection area c of the negative electrode 123and the substrate wiring 107. The distance from the end of the TFTsubstrate 100 to the connection area c is mounting margin a+margin d ofadhesive 301+connection area c. With this structure, the dimension ofthe non-display area at the periphery of the display device 1 is large.

Contrarily, with the structure of the first embodiment depicted in FIG.2, the negative electrode 123 or the connection area c of the negativeelectrode 123 and the wiring 107 is placed into the lower part area(width d) of the sealing portion 202. The distance from the end of theTFT substrate 100 to the cornices ton area is mounting margin a+margin dof adhesive 301. Margin d of the adhesive 301 will be approximately b+c,and the dimension of the non-display area will be reduced in an amountcorresponding to the margin c of the wiring connection portion.

Moreover, with the structure of the first embodiment, the lower partarea of the sealing portion 202 is formed, as shown in FIG. 5(a), to bepractically flat, or such that the unevenness does not change. In FIG.5(a) and FIG. 5(b), the components corresponding to those illustrated inFIG. 2 are given the same reference numerals, and the explanation ofsuch components is omitted.

In FIG. 5(a) and FIG. 5(b), x represents the connection width of thepower source wiring 107 and the common electrode film 123, y representsthe misalignment between the power source wiring 107 and the commonelectrode film 123, and z represents the sealing margin under thesealing area at the periphery of the foregoing connection area.

As illustrated in these diagrams, the power source wiring 107 of the TFTsubstrate 100 at the lower part area of the sealing portion 202 isformed to be relatively broad and flat. The power source wiring 107 is,as shown in FIG. 1, disposed at the periphery of the substrate 100 so asnot to intersect with other wirings. Thereby, the generation ofunevenness arising from the intersecting of wirings is avoided as muchas possible, and the power source wiring 107 is formed to be flat. Thealuminum film 112 and ITO film 121 are formed flatly thereon andaluminum of the common electrode film 123 is further deposited on theflat face 1 of these conductive films in order to realize electricalconnection with the negative electrode of the light emitting clement120. The top face (insulation film 111) m of the substrate 100 at theperipheral side of this connection area is also formed to be flat.

Preferably, as shown in FIG. 5(a), the misalignment y between the powersource wiring 107 and the common electrode film 123 is made to be 0.Thereby, the width of the power source wiring 107 and the connectionwidth of the common electrode 123 are coincided to minimize wiringresistance, and, as a result, the waste of measurement in the widthdirection can be avoided.

As described above, the conductive portion (vertical conductive portion)x of the power source wiring film 107 and the common electrode 123 isformed to be flat, and the sealing area z of the periphery thereof isalso made to be a flat area. Vertical conduction is carried out withcertainty, unevenness of the film end portion after forming the commonelectrode film 123 is evenly formed, and height of the verticalconductive portion is aligned at the TFT substrate 100 side so as toprevent the sealing conditions from changing in the vertical conductivearea portion. Further, by securing a flat portion z at the peripheralportion z of the vertical conductive portion x, the stress applied tothe sealing portion from can sealing can be made uniform.

FIG. 6(a) to FIG. 6(d) are process charts for explaining themanufacturing process of the display device 1 according to the firstembodiment.

Foremost, as shown in FIG. 6(a), the TFT substrate 100 is formed. Inother words, a silicon nitride film is deposited on the glass substrate101 with the CVD method in order to form the protective film 102.Silicon is deposited thereon with the CVD method. Further,low-concentration impurities are injected therein, and thermalprocessing of laser annealing is performed thereto in order to form thepolysilicon film 103. Pattering is performed to this polysilicon film103 in order to form the TFT area 130. The gate insulation film 104formed from oxidized silicon is deposited thereon wish the CVD method.Aluminum is deposited thereon with the sputtering method and patterningis performed thereto in order to form organic EL driving power sourcewiring films 105 and 106, the organic EL negative electrode wiring layer107, and the gate wiring film 108 of the TFT 130. Next, a mask is usedto inject high-concentration ion into the source drain area of the TFTarea 103, and the impurities are activated with thermal processing.Further, oxidized silicon is deposited thereon with the CVD method inorder to form the first interlayer insulation film 110. A contact holemask is used to perform anisotropic etching to this interlayerinsulation film 110 in order to open a contact hole in the source drainarea of the TFT area 103. Next, aluminum is deposited thereon andpattering is performed thereto in order to from the source drainelectrode 109 and the connection electrode 112.

Next, as shown in FIG. 6(b), oxidized silicon is deposited thereon inorder to form the second interlayer insulation film 111. Etching isperformed to the interlayer insulation film 111 on the wiring film 107in order to expose the aluminum film 112. ITO is deposited thereon withthe sputtering method, and pattering is performed thereto in order toform the positive electrode 121 of the light emitting element 120.Moreover, the ITO film 121 is also deposited on the aluminum film 112 onthe wiring film 107 in order to adjust the film thickness of theconnection area and to prevent oxidization of the aluminum surface.

As shown in FIG. 6(c), a photosensitive organic resin film is appliedwith the spin coating method, and pattering is performed thereto inorder to form the bank layer 113 in which the positive electrode (ITO)121 of the light emitting element is exposed at the bottom part of thegroove. This bank layer 113 separates the respective light emittingelements. Next, the EL layer 122 is formed on the positive electrode 121with the inkjet method. The EL layer 122 is structured, for example,from a light emitting layer, electron transport layer, electroninjection layer, hole injection layer, hole transport layer, and so on.Calcium 123a, for instance, is patterned on these light emittingelements 120 with vacuum deposition, and patterning is further performedthereto by evaporating the aluminum 123b. Calcium 123a and aluminum 123bstructure the negative electrode (common electrode) 123 of the lightemitting element 120. By making the negative electrode 123 a two-layerstructure covered with the lower layer calcium layer 123a and the upperlayer aluminum layer 123b, infiltration of moisture to the calcium film123a is prevented (securement of gas barrier properties). The aluminumfilm 123b is spread out to the periphery of the substrate 101 as thecommon electrode 123, and is connected to the wiring film 107 via theITO film 121 and the aluminum film 112 at the margin c of the wiringconnection portion (c.f. FIG. 2).

Next, as shown in FIG. 6(d), an adhesive or sealant 301 is applied tothe portion including the wiring film 107 at the periphery of the TFTsubstrate 100, and the sealing substrate 200 having an inverted concaveshape with protrusions 202 at the periphery thereof is bonded under aninert gas atmosphere such as nitrogen gas. A drying agent is disposedinside the sealing substrate 200, and adsorbs the moisture or oxygeninfiltrating inside. As the adhesive, preferably used is an insulationmaterial that does not permeate oxygen or moisture, and photo-curingresin or thermosetting resin may be used. For example, epoxy resin oracrylate resin may be used.

The display device is formed as described above.

The second embodiment is illustrated in FIG. 7 and FIG. 8. In thesediagrams, the components corresponding to those illustrated in FIG. 2and FIG. 3 are given the same reference numerals, and the explanation ofsuch components is omitted.

In the present embodiment, a flat substrate is used as the sealingsubstrate 200. As the scaling substrate 200, preferably employed may bea glass plate, aluminum plate, stainless plate, acryl plate, ceramicplate, and so on. The adhesive 301 is used to fill the entire gapbetween the TFT substrate 100 and the sealing substrate 200 so as tojoin (bond) the two substrates. Even in this case also, the width ofmargins b+c necessary in securing the reliability of sealing describedabove including the connection area of the negative electrode 123 andthe wiring film 107 of the substrate is secured, and the bank layer 113is positioned to be inside the connection area of the negative electrode123 and the wiring film 107 of the substrate. Thereby, the frame widthcan be narrowed, and, infiltration of gas into the bank layer 113 can beprevented as a result of placing the resin film 113, which hasrelatively high moisture permeability, away from the adhesive 301.

FIG. 9(a) to FIG. 9(d) are process charts for explaining themanufacturing process of the display device 1 according to the secondembodiment. In these diagrams, the components corresponding to thoseillustrated in FIG. 6 are given the same reference numerals, and theexplanation of such components is omitted.

In this display device also, the processes of FIG. 9(a) to FIG. 9(c) aresimilarly conducted as with FIG. 6(a) to FIG. 6(c).

As shown in FIG. 9(c), after the TFT substrate 100 is formed, theadhesive 301 is applied to the top face of the TFT substrate 100 withthe spin coating method, ink-jet method or transcription roller toachieve a suitable film thickness. The sealing substrate 200 is bondedon top of this adhesive film while being aligned with the TFT substrate100.

Moreover, the adhesive 301 may also be applied to the sealing substrate200 for bonding with the TFT substrate 100. Further, after aligning thesealing substrate 200 and the TFT substrate 100, an adhesive may beinfiltrated inside from the peripheral gaps with the capillaryphenomenon.

The third embodiment is illustrated in FIG. 10 and FIG. 11. In thesediagrams, the components corresponding to those illustrated in FIG. 2and FIG. 3 are given the same reference numerals, and the explanation ofsuch components is omitted.

In the present embodiment, a multilayer thin film 210 is formed insteadof the scaling substrate 200. For example, Japanese Patent Laid-OpenPublication No. 2000-223264 proposes a laminate film of an inorganicpassivation sealing film and resin sealing film as the sealing film. Themultilayer thin film 210 is formed on the TFT substrate 100, and coversthe negative electrode 123 in its entirety. The multilayer thin film mayadopt the various structures; for instance, the structure of an organiclayer/inorganic layer/organic layer, or inorganic layer/organiclayer/inorganic layer, and so on. As the inorganic material, forexample, ceramic materials such as SiO₂, SiN and SiON may be used, and,as the organic resin material, general hydrocarbon macromolecules suchas polyethylene, polystyrene and polypropylene may be used. Moreover,this may also be fluoric macromolecules. The polymer materialsthemselves may be disposed, or precursors or monomers may be applied onthe substrate for curing. The negative electrode 123 is connected to thepower source wiring 107 at the end side of the substrate 100. Even inthis case also, the width of margins b+c necessary in securing thereliability of sealing described above including the connection area ofthe negative electrode 123 and the wiring film 107 of the substrate issecured, and the bank layer 113 is positioned to be inside theconnection area of the negative electrode 123 and the wiring film 107 ofthe substrate. Thereby, the frame can be narrowed.

FIG. 12(a) to FIG. 12(d) are process charts for explaining themanufacturing process of the display device 1 according to the thirdembodiment. In these diagrams, the components corresponding to thoseillustrated in FIG. 6 are given the same reference numerals, and theexplanation of such components is omitted.

In this display device also, the processes of FIG. 12(a) to FIG. 12(c)are similarly conducted as with FIG. 6(a) to FIG. 6(c).

As shown in FIG. 12(c), after the TFT substrate 100 is formed, as shownin FIG. 12(d), a highly airtight protective film 210 is used to coverthe TFT substrate 100 so as to prevent the negative electrode 123 frombeing exposed to the outside air, and patterning is performed to theperiphery thereof in order to enable separation of the substrate. Theprotective film 210 is preferably a multilayer thin film. As describedabove, the multilayer thin film may be formed by laminating an organiclayer/inorganic layer/organic layer, or inorganic layer/organiclayer/inorganic layer, and so on. As the inorganic material, forexample, ceramic materials such as SiO₂, SiN and SiON may be used, and,as the organic resin material, general hydrocarbon macromolecules suchas polyethylene, polystyrene and polypropylene may be used. Moreover,this may also be fluoric macromolecules. The polymer materialsthemselves may be disposed, or precursors or monomers may be applied onthe substrate for curing.

FIG. 13 illustrates the fourth embodiment of the present invention. Inthe present embodiment, an example is illustrated where dummy pixels arefurther added to the display area of the display device of the foregoingfirst to third embodiments.

Gas infiltrated inside the display device will penetrate within the filmand affect the display area from the display elements on the peripheralside. Thus, by providing in advance dummy pixels that are not used inimage display at the periphery of the display area, influence of theinfiltrated gas to the screen display is alleviated. Moreover, as aresult of providing dummy pixels at the periphery of the display area,the applied film can be formed evenly when a luminous material isapplied with the inkjet method. In other words, with the inkjet method,minute ink (material) droplets are discharged from the nozzle, and,after the start of such discharge, time is required for the dischargedrate to become stable. As a result of stabilizing the discharge rate atthe dummy pixel portion, the coating film of the respective lightemitting elements can be made uniform.

Moreover, the mask deposition method may also be employed instead of theinkjet method for forming the luminous body. Further, the inkjet methodand mask deposition method may be used in combination.

FIG. 14 to FIG. 17 illustrate yet other embodiments of the presentinvention. In the respective diagrams, the components corresponding tothose illustrated in FIG. 1 are given the same reference numerals, andthe explanation of such components is omitted.

In these embodiments, although the TFT substrate and the sealingsubstrate are placed together and sealed at the periphery of thesubstrates, one or more sides, or all of the sides of the periphery ofthe TFT substrate are narrowed.

With the embodiment illustrated in FIG. 1 and FIG. 2, as shown in FIG.14, the power source wiring 107 and the common electrode (negativeelectrode) 123 are connected as the three sides (upper side, left side,right side) of the square (polygonal) substrate 100, narrowing of theframe is sought by sealing the outside areas thereof, and the driver IC(external circuit) is connected with the wiring tape 402 as one side(lower side). According to this structure, wiring resistance can bereduced up to the common electrode 123 with the connection at threesides, and, since one side can be dedicated to connection with theexternal circuit, the frame of the overall display device module can benarrowed in a well-balanced manner.

With the embodiment illustrated in FIG. 15, the power source wiring 107and the common electrode (negative electrode) 123 are connected at oneside (lower side) of the substrate 100, and sealing is performed at theoutside area thereof. In this example, since the common electrode 123and the wiring film 107 are connected at only one side, it is difficultto narrow the frame since a sufficient conductive area (verticalconductive area) must be secured between the common electrode 123 andthe wiring film 107 with this one side. Nevertheless, since the wiringwith the common electrode 123 will no longer be necessary at the otherthree sides, the frame portion of such three sides can be narrowedsignificantly. This kind of structure is effective in cases as with adisplay device of a portable telephone wherein the module may beelongated in a certain direction, but is restricted in other directions.

With the embodiment illustrated in FIG. 16, the common electrode 123 andthe wiring film 107 are connected at two sides (left side and rightside) of the substrate 100, and sealing is performed respectively to theoutside areas thereof. When providing the wiring tape 402 to either side(upper side and lower side) facing each other, respectively, in order toinstall an external circuit, for instance, this is effective whendriving the odd number lines from the top and driving the even numberlines from the bottom, and a large capacity (large screen) display isenabled by mounting numerous driver ICs. Moreover, with this structure,the reduction of wiring resistance comparable with the case ofconnecting the common electrode 123 and the wiring film 107 at threesides as depicted in FIG. 14 may be sought.

With the embodiment illustrated in FIG. 17, the common electrode 123 andthe wiring film 107 are connected at four sides (upper side, lower side,left side, right side) of the substrate 100, and sealing is performedrespectively to the outside areas thereof. Then, a pullout wiring isformed via the insulation film at the lower part of the wiring forseeking conductivity between the common electrode 123 and the wiringfilm 107 with the multilayer wiring film, and this wiring is connectedwith an external circuit. Moreover, the conductive area for connectingthe common electrode 123 and the wiring film 107 may be separated into aplurality of blocks, and a pullout wiring may be disposed between themutual blocks. According to this kind of structure, sufficient reductionof wiring resistance required for realizing a large-size high resolutiondisplay can be attained.

As described above, according to the respective embodiments of thepresent invention, since the display device is assembled such that theconnection area (c) of the common electrode (negative electrode) 123 andthe substrate wiring 107 is included within the sealing margin (b+c),the frame area of the display unit can be reduced.

Moreover, since the bank layer 113 is positioned to be further insidethe substrate than the connection area (c) of the common electrode 123and the substrate wiring 107, it is possible to prevent gas fromdirectly penetrating within the bank layer 113 from the connectionportion (b+c) of the substrate 100 and the sealing substrate (or sealingfilm) 200. Thereby, influence on the light emitting element 120 will beminimal even upon employing a resin (such as a photoresist), which canbe processed easily, as the bank layer 113.

Moreover, as a result of placing the calcium electrode 123a away fromthe connection area (c) of the electrode 123a and the substrate wiring107, erosion of the calcium electrode 123a due to infiltration of oxygenor water vapor gas can be prevented.

Next, electronic devices comprising the display device according to thepresent invention are described below. The present invention, however,shall in no way be limited to these exemplifications.

<Mobile Computer>

Foremost, an example employing the display device pertaining to theforegoing embodiments in a mobile personal computer is explained. FIG.18 is a perspective view showing the structure of this personalcomputer. In FIG. 18, the personal computer 1100 is structured from amain body 1104 comprising a keyboard 1102, and a display device unitcomprising the foregoing display device 1106.

<Portable Phone>

Next, an example of employing the display device pertaining to theforegoing embodiments in the display unit of a portable telephone isexplained. FIG. 19 is a perspective view showing the structure of thisportable telephone. In FIG. 19, the portable telephone 1200 comprises aplurality of operation buttons 1202, an earpiece 1206, a mouthpiece1024, and the foregoing display device 1208.

<Digital Still Camera>

An example of employing the display device pertaining to the foregoingembodiments in the finder of a digital still camera is now explained.FIG. 20 is a perspective view showing the structure of this digitalstill camera, and also briefly shows the connection with externalequipment.

Whereas an ordinary camera exposes the film with the optical image ofthe photographic subject, the digital still camera 1300 generates imagesignals by performing photoelectric conversion to the optical image ofthe photographic subject with visual elements of a CCD (Charge CoupledDevice) or the like. The foregoing display device 1304 is provided tothe back face of the case 1302 of this digital still camera 1300, and isstructured to conduct display based on the visual signals from the CCD.Thus, the display device 1304 functions as a finder for displaying thephotographic subject. Moreover, a light receiving unit including thelikes of an optical lens or CCD is provided to the observation side ofthe case 1302.

When the photographer confirms the image of the photographic subjectdisplayed on the display device 1304 and presses the shutter button1308, the visual signal of the CCD at such moment is transmitted to andstored in the memory of the circuit substrate 1310. Moreover, thisdigital still camera 1300 also comprises a video signal output terminal1312 and a data transmission I/O terminal 1314 at the side face of thecase 1302. And, as illustrated in FIG. 20, a television monitor 1330 isconnected to the video signal output terminal 1312 and a personalcomputer 1340 is connected to the data transmission I/O terminal 1314,respectively, as necessary. Further, pursuant to prescribed operations,the structure is such that the visual signal stored in the memory of thecircuit substrate 1308 is output to the television monitor 1330 or thecomputer 1340.

<Electronic Book>

FIG. 21 is a perspective view showing the structure of an electronicbook as an example of the electronic device according to the presentinvention. In FIG. 21, reference numeral 1400 represents the electronicbook. The electronic book 1400 comprises a book-shaped frame 1402 and acover 1403 capable of opening and closing this frame 1402. A displaydevice 1404 is provided to the frame 1402 in a state where its displayface is exposed to the surface thereof, and, an operation unit 1405 isalso provided thereto. A controller, counter, memory and so on are builtin the frame 1402. In the present embodiment, the display device 1404comprises a pixel portion to which display elements are disposed and anintegrated peripheral circuit that is provided integrally with suchpixel portion. The peripheral circuit comprises a decoder scan driverand data driver.

Moreover, as the electronic device, in addition to the personal computerof FIG. 18, the portable telephone of FIG. 19, the digital still cameraof FIG. 20 and the electronic book of FIG. 21, electronic paper, liquidcrystal televisions, view-finding or monitor-viewing video taperecorders, car navigation devices, pagers, electronic notebooks,calculators, word processors, workstations, television phones, OSterminals, devices comprising a touch panel and so on also apply. And,the foregoing display device may be employed as the display unit of therespective electronic devices described above.

The display device according to the present invention is not limited tothe organic EL display device of the embodiments. Moreover, thesubstrate is not limited to the TFT substrate of the embodiments. Inaddition to an active substrate, the present invention can also beemployed in a passive substrate.

Moreover, although an adhesive was used as the joining means in theembodiments, it is not limited thereto. Other methods, for instance,joining with supersonic waves or lasers may also be employed.

As described above, according to the display device of the presentinvention, it is preferable in that the width of the frame, which is thenon-display area at the periphery of the display area, can be narrowed.

1. A display device, comprising: a substrate including a plurality ofdisplay elements, a bank layer that separates each of the displayelements, and a wiring layer; a common electrode layer that is spreadout to the periphery of the substrate and covers said plurality ofdisplay elements and said bank layer; and a multilayer thin film forcovering the substrate, wherein a flat peripheral portion of the commonelectrode layer is laminated to a flat top face of the wiring layerthrough laminated flat conductive films which form a linear electricalconnection area in plane, and the connection area is continuouslypositioned outside of the bank layer along sides of the substrate wherea wiring tape is not connected, and the multilayer thin film extendsbeyond the connection area of the common electrode layer and the wiringlayer.
 2. The display device according to claim 1, wherein at least onethin film among the multilayer thin film has gas barrier properties oranti-environmental properties.
 3. The display device according to claim1, wherein the substrate is a square substrate, and the common electrodelayer and the wiring layer are connected at one side of the substrate bylaminating the common electrode layer and the wiring layer togetherusing the laminated flat conductive films.
 4. The display deviceaccording to claim 1, wherein the substrate is a square substrate, andthe common electrode layer and the wiring layer are connected at twosides of the substrate by laminating the common electrode layer and thewiring layer together using the laminated flat conductive films.
 5. Thedisplay device according to claim 1, wherein the substrate is a squaresubstrate, and the common electrode layer and the wiring layer areconnected at three sides of the substrate by laminating the commonelectrode layer and the wiring layer together using the laminated flatconductive films.
 6. The display device according to claim 1, whereinthe multilayer thin film includes an inorganic layer.
 7. The displaydevice according to claim 6, wherein the inorganic layer is made of amaterial selected from SiO₂, SiN and SiON.
 8. The display deviceaccording to claim 1, wherein the multilayer thin film includes anorganic layer.
 9. The display device according to claim 8, wherein theorganic layer includes fluoric macromolecules.
 10. The display deviceaccording to claim 8, wherein the organic layer is made of a materialselected from polyethylene, polystyrene and polypropylene.
 11. Thedisplay device according to claim 1, wherein the multilayer thin film isformed by laminating an organic layer/inorganic layer/organic layer. 12.The display device according to claim 1, wherein the multilayer thinfilm is formed by laminating an inorganic layer/organic layer/inorganiclayer.
 13. A manufacturing method of a display device, comprising: astep of forming at least a wiring layer at a part of the periphery of asubstrate to which an electrical circuit is to be formed; a step offorming an element separation layer comprising a plurality of groovesfor mutually separating a plurality of display elements excluding anarea over the wiring layer of the substrate; a step of forming saiddisplay elements to each of the plurality of grooves of the elementseparation layer; a step of forming a common electrode layer on theplurality of display elements, the element separation layer, and thewiring layer, respectively; and a sealing step of directly forming amultilayer thin film above the common electrode layer and the substrate;wherein a flat peripheral portion of the common electrode layer islaminated to a flat top face of the wiring layer through laminated flatconductive films which form a linear electrical connection area inplane; and the connection area is continuously positioned outside of theelement separation layer along sides of the substrate where a wiringtape is not connected, and the multilayer thin film extends beyond theconnection area.
 14. A display device comprising: a substrate having adisplay area, a first connection area that is positioned between thedisplay area and a first edge of the substrate, and a second connectionarea that is positioned between the display area and a second edge ofthe substrate; a first electrode disposed in the display area; a secondelectrode disposed above the display area, the first connection area,and the second connection area; a light emitting layer disposed betweenthe first electrode and the second electrode; and a wiring electricallyconnected to the second electrode in the first connection area and thesecond connection area, and the wiring having a first portion thatextends along the first edge of the substrate and a second portion thatextends along the second edge of the substrate, the wiring electricallycontacting the second electrode along the first edge and the secondedge.
 15. The display device according to claim 14, further comprising:an interlayer insulation film disposed in the display area, between thedisplay area and the first connection area, and between the display areaand the second connection area, wherein the first portion of the bankand the second portion of the bank are disposed on the interlayerinsulation film.
 16. The display device according to claim 14, aconductive layer being disposed between the wiring and the secondelectrode.
 17. The display device according to claim 14, the wiringbeing electrically connected to the second electrode continuously alongat least a portion of the edge.
 18. The display device according toclaim 14, the first portion of the wiring being spaced apart from thefirst edge and the second portion of the wiring being spaced apart fromthe second edge.
 19. A display device comprising: a substrate having adisplay area, a first connection area that is positioned between thedisplay area and a first edge of the substrate, and a second connectionarea that is positioned between the display area and a second edge ofthe substrate; a first electrode disposed in the display area; a secondelectrode disposed above the display area, the first connection area,and the second connection area; a light emitting layer disposed betweenthe first electrode and the second electrode; a wiring electricallyconnected to the second electrode in the first connection area and thesecond connection area; and a bank having a first portion disposed inthe display area and a second portion disposed between the display areaand the first connection area, the second portion being in anon-overlapping condition with the first connection area, and the wiringhaving a first portion that extends along the first edge of thesubstrate and a second portion that extends along the second edge of thesubstrate, the wiring electrically contacting the second electrode alongthe first edge and the second edge.
 20. The display device according toclaim 19, further comprising: an interlayer insulation film disposed inthe display area, between the display area and the first connectionarea, and between the display area and the second connection area,wherein the first portion of the bank and the second portion of the bankare disposed on the interlayer insulation film.
 21. A display devicecomprising: a substrate having a display area, a first connection areathat is positioned between the display area and a first edge of thesubstrate, and a second connection area that is positioned between thedisplay area and a second edge of the substrate; an interlayerinsulation film disposed between the display area and the firstconnection area; a first electrode disposed in the display area; asecond electrode disposed above the display area, the first connectionarea, and the second connection area; a light emitting layer disposedbetween the first electrode and the second electrode; a wiringelectrically connected to the second electrode in the first connectionarea and the second connection area; and a bank disposed on theinterlayer insulation film between the display area and the firstconnection area, the first connection area being disposed to the outsideof the bank, and the wiring having a first portion that extends alongthe first edge of the substrate and a second portion that extends alongthe second edge of the substrate, the wiring electrically contacting thesecond electrode along the first edge and the second edge.
 22. Thedisplay device according to claim 21, wherein the first connection areafollows a first edge of the bank and the second connection area followsa second edge of the bank.
 23. The display device according to claim 21,wherein the display area is disposed to an inside of the bank.
 24. Adisplay device comprising: a substrate having a first side opposite froma second side, and a third side opposite from a fourth side; a pluralityof data lines disposed above the substrate; a plurality of firstelectrodes disposed above the substrate; a second electrode opposite tothe plurality of the first electrodes; a plurality of light emittingelements disposed between the plurality of the first electrodes and thesecond electrode; a first wiring following the first side of thesubstrate, the first wiring connected to the second electrode; a secondwiring following the second side of the substrate, the second wiringconnected to the second electrode; a first wiring tape attached to thethird side of the substrate; and a second wiring tape attached to thefourth side of the substrate.
 25. The display device according to claim24, the plurality of light emitting elements being separate from eachother.
 26. A display device comprising: a substrate including: aplurality of display elements, a bank layer that separates each of thedisplay elements, and a wiring layer; and a common electrode layer thatis spread out to a periphery of the substrate and that covers theplurality of display elements and the bank layer, wherein a flatperipheral portion of the common electrode layer is laminated to a flattop face of the wiring layer through laminated flat conductive filmswhich form a linear electrical connection area in a plane, and theconnection area is continuously positioned outside of the bank layeralong the sides of the substrate.